PARTING SHOT Possessive Pose

THE FEMALE SHREW’S FEAT OF REARING ITS YOUNG CONTINUES TO AMAZE ME.

ical studies on shrews during the cold months, my graduate students and I have been unable to find evidence that shrews ever slow down. We now suspect that one way they survive Montana’s -30 degree temperatures is by staying in the small, rela tively warm space between the ground and the snowpack. They search for food in this insulated environment, which rarely gets colder than 35 degrees regardless of the air temperature above. Shrews also stay warm—and conserve precious calories—by growing a winter coat of dense hair. How they stay fed that time of year is still a mystery. Seeds and other plant material don’t have enough protein, so shrews must continue to live on insects during the cold months. We suspect that overwintering grubs provide them with a rich source of fat and protein.

AMAZING REPRODUCTION If a shrew survives the winter, its breeding activity begins in March and peaks in April or May. Most shrew species typically produce four to seven young after a 20-day gestation period. Young shrews grow extremely fast. The newborn masked (common) and vagrant shrews we rear in our laboratory grow to nearly adult size in roughly three weeks. The poor mother must produce milk for babies each growing to over 3 grams before they are weaned. That’s 12 to 21 grams of babies fed by a female who herself weighs only 4 grams. As a longtime mammalogist, I know that animals can do some remarkable things, but the female shrew’s feat of rearing its young continues to amaze me. What’s more, females may even produce an additional litter during their second summer. Both males and females age rapidly and die in the fall. At just 16 to 18 months long, shrews have one of the shortest life spans of any mammal.

Though shrews are found throughout Montana, they are so small and well camouflaged by their gray or brown fur that people rarely see them. Those interested in watching shrew behavior should look under logs on moist forest floors dense with decaying wood and leaves. This habitat provides shrews with a rich source of insect food and ideal protective cover.

All shrew species have poor eyesight, but they compensate with keen senses of smell and hearing. They have long nasal passages, a flexible nose that constantly moves in different directions, and highly developed whiskers sensitive to vibrations in the soil. A shrew uses its snout to probe leaf litter or loose soil for worms or insects. Some species, such as the vagrant shrew, may also find prey using a primitive form of echolocation. Like bats, these shrews emit high-frequency squeaks. We suspect that they can judge distance by hearing their ultrasounds echoing back from objects ahead of them. I find all shrews fascinating but the northern water shrew particularly so.

Common throughout western Montana, it is the largest shrew in North

America. The species prefers watery habitat, especially cascading mountain streams. Northern water shrews forage underwater on aquatic insects and often build their nests on moss-covered rocks in midstream. Scientists suspect that this shrew has evolved to be larger than others to survive in cold water. (The larger a mammal’s size, the less surface area it has relative to body mass, meaning less heat loss.) Unlike other shrews, the northern water shrew has long, coarse hairs growing between its toes. The hairs intertwine to create a weblike surface that powers the shrew’s swimming strokes. It’s no surprise that northern water shrews have adapted to survive in their unique environments. That’s true of all shrews. These tenacious little warriors evolved millions of years ago and have survived everything nature could throw at them, from ice ages to floods to supervolcanic eruptions. Yet here they remain, dashing back and forth across the forest floor at breakneck speed, hunting, always hunting.

DONALD RUBBELKE

READY TO EAT, AGAIN Due to a high metabolism that burns their entire body weight in calories each day, shrews must constantly feed on spiders and other insects. If they go for more than one hour without food, they risk starving.

ALEX BADYAEV

Western (Boreal) Toad (Bufo boreas)

SAM STEWART, BONTERRA CONSULTING 2008

By John Fraley

W

estern Montana is home to only one toad species, the western toad. (Montana’s other two toads, Woodhouse’s and the Great Plains, live east of the Continental Divide.) The Montana form of the western toad is known as the boreal toad. Along with two other subspecies, it is found across the Pacific Northwest from southern California to Alaska. In Montana, it ranges from the Idaho border to the Rocky Mountain Front and even farther east in the Little Belt, Crazy, and Absaroka mountains.

These plump toads are adaptable amphibians. I’ve seen them around low-elevation lakes and woods but also in the high country of the Great Bear Wilderness, at the top of Lone Man Mountain in Glacier National Park, and on Columbia Mountain in the Swan Mountain Range. In fact, western toads have been found living at over 9,000

John Fraley manages the FWP Regional Information and Education Program in Kalispell. feet in the Madison Range. Kirwin Werner, a herpetologist and senior author of Am phibians and Reptiles of Montana, has en countered them on the Continental Divide in Glacier National Park, 1,500 feet above any water source. “You wonder how they got up there,” he says.

Appearance This squat, bloated-looking toad is 3 to 5 inches long. Its back is olive to brown, and the light green, whitish, or gray belly is covered in spots. A white stripe runs down the center of the back from the nose to the anus. The skin is covered with warts of various shapes and sizes. Females are larger than males and have a rougher and more blotchy skin. The boreal toad can absorb water through its smooth belly skin, and the bumpy skin on its back prevents drying. Boreal toads have big, gogglelike eyes, with large parotoid glands behind their eyes. The glands secrete a milky substance that is toxic to predators.

Sound Male western toads emit a series of high-pitched chirps, similar to the sound made by young geese. Herpetologists suspect the toad chirps to attract a mate during the spring breeding season or to tell other males to stay away.

Food Boreal toads eat flies, ants, spiders, and dragonflies. Adults occasionally eat young toads or other small amphibians.

Reproduction In spring, boreal toads breed in puddles and pond and lake shallows. A male grasps a female with his thumb pads and then mounts her. The female lays thousands of eggs in a long string, which the male fertilizes as they exit her body. The eggs hatch in a week or two. The small, dark tadpoles remain in large groups before dispersing after they metamorphose into half-inch-long young toads. The toads be come sexually mature after about four years.

Habitat Boreal toads live in a wide range of wet habitats, including forests, meadows, uplands, and marshy areas at nearly all elevations. They are mostly nocturnal but can be found during the day in cool weather or at higher elevations. Boreal toads hibernate in winter. They hibernate—and find refuge from summer heat—under logs, in rodent burrows, or by burying themselves in soft duff or dirt, sometimes more than a mile from water. Boreal toads have horny tubercles on their hind feet that aid in digging.

Behavior Unlike frogs, which leap from place to place, boreal toads shuffle along or move in short hops. When handled or threatened, they puff up, urinate, or emit a foul-smelling secretion from their warts. The secretion deters most predators, though coyotes, raccoons, snakes, ravens, and crows are known to eat boreal toads.

Status in Montana Boreal toads are found in many areas throughout western Montana, but no one is sure how the state’s overall population is faring. Werner says that based on his observations, the population seems “fairly stable.” But the Montana Nat ural Her itage Program notes that numerous surveys since the early 1990s indicate declining populations in some parts of western Mon tana. The state has listed the boreal toad as a “species of concern.”

PARTING SHOT

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Demonstrating a behavior known as “mantling,” a Harris’s hawk spreads its wings and tail to hide freshly killed prey from other predators. See page 8 to learn how dedicated Montana falconers use these and other raptors to hunt. Photo by Kate Davis.

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MARCH–APRIL 2009 VOLUME 40, NUMBER 2

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